docs: def objects(self, cls=None):
          """
          Return an iterater over all objects in this directory which are
          instances of `cls`. By default, iterate over all objects (`cls=None`).
  
          Parameters
          ----------
  
          cls : a class, optional (default=None)
              If a class is specified, only iterate over objects that are
              instances of this class.
  
          Returns
          -------
  
          A generator over the objects in this directory.
  
          Examples
          --------
  
              $ rootpy browse myfile.root
  
              In [1]: list(f1.objects(R.Directory))
              Out[1]: [Directory('mydirectory')]
  
          """
          objs = (asrootpy(x.ReadObj(), warn=False)
                  for x in self.GetListOfKeys())
          if cls is not None:
              objs = (obj for obj in objs if isinstance(obj, cls))
          return objs